Hydrogen cyanide (HCN) featured with high volatility and high adsorption is a common toxic and hazardous gas. Traces of HCN are also found in human exhaled breath. Unusual high HCN concentration in the breath of cystic fibrosis (CF) patients is associated with Pseudomonas aeruginosa (PA) infection. Therefore, the development of a highly sensitive online HCN measurement in exhaled breath can enable rapid screening for PA infection in CF patients.
　　Recently, a research group led by Prof. LI Haiyang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has developed a flow-assisted photoionization mass spectrometry method for profiling hydrogen cyanide in exhaled breath.
　　The study was published in Analytical Chemistry on April 4.
　　Schematic diagram of the vacuum ultraviolet lamp-based negative photoionization source and detected human exhaled HCN profile (Image by Wen Yuxuan)
　　"HCN is easily soluble in water and highly adsorbed on device surfaces, so sensitivity and response speed are main challenges for directly measuring HCN in exhaled breath at high humidity presents," said Prof. CHEN Ping, co-corresponding authors of this study.
　　The researchers developed a method by utilizing a self-developed atmospheric pressure negative photoionization time-of-flight mass spectrometer instrument and improved the sensitivity and time resolution of direct HCN measurements in exhaled breath. This method enabled real-time tracking of HCN concentrations in a single exhaled breath, which could provide an effective means for early screening of CF patients with PA infection.
　　They proposed to use helium shield gas within the mass spectrometry ionization source. This approach reduced the effect of high humidity on ionization, improved ion transport efficiency, and thus enhanced HCN detection sensitivity.
　　Moreover, they improved the sampling system by shortening the sampling line and adding a gas purging process to effectively reduce HCN adsorption residue and improve time resolution. This method achieved a limit of detection of 0.3 ppbv and a resolution time of 0.5 s.
　　By utilizing this method, the researchers tracked the changes in the single exhaled HCN profiles of volunteers before and after gargling. The resulting profiles clearly showed an early peak and a stable end-tidal plateau, representing the concentration of the oral cavity and end-tidal gas， respectively.
　　"The new method demonstrated good resistance to interference and high accuracy in HCN quantification. It has potential application in the detection of PA infection in CF patients," said Prof. LI.

　　Two notable metal oxide structures, spinel-type oxide and solid solution-type oxide, are widely used in Oxide-Zeolite (OXZEO) bifunctional catalysts for CO/CO2 hydrogenation reactions.
　　Identifying the crystallographic structure sensitivity of catalysts in chemical reactions is helpful to the rational design of catalysts. However, direct and convincing study to correlate the crystal structure of oxide to its catalytic performance is still lacking.
　　Recently, a joint research team led by Prof. BAO Xinhe, Prof. PAN Xiulian, Assoc. Prof. JIAO Feng and Prof. XIAO Jianping from the Dalian Institute of Chemical Physics(DICP) of the Chinese Academy of Sciences (CAS) has observed the strongly crystal phase-dependent activity of MnGaOx in direct syngas conversion.
　　This study was published in Angewandte Chemie International Edition on April 18.
　　"The main challenge to observing the crystal structure of oxide is the lack of a well-defined material-synthesis method to obtain metal oxides with the same element components but different crystallographic structures," said JIAO.
　　In this study, the researchers found co-precipitation method and hydrothermal method could synthesize bimetallic oxides, which were composed of amorphous MnO2 and Ga2O3 with hexagonal close-packed (HCP) or Face centered-cubic (FCC) crystal phase, respectively. More interestingly, they found that the HCP oxide remained unchanged as HCP MnO-Ga2O3 solid solution oxides after reduction under H2 or CO, while the FCC solid solution oxide transformed into FCC spinel structure, where reduced Mn2+ took the A-site of AB2O4 spinel structure.
　　Crystal-phase-dependent of syngas conversion activity of MnGaOx-SAPO-18 (Image by BAI Bing and JIAO Feng)
　　They obtained 40% CO conversion, 81% light olefins selectivity, and 0.17 g·gcat-1·h-1 space-time yield of light olefins with the combination of FCC MnGaOx-Spinel and SAPO-18. In comparison, they obtained a much inferior activity with solid solution MnGaOx with a similar chemical composition.
　　They further proved that the superior activity of MnGaOx-Spinel was attributed to its higher reducibility and the presence of coordinatively unsaturated Ga3+ site, which facilitated the dissociation of the C-O bond via a more efficient ketene-acetate pathway to light olefins.
　　"Our findings may further optimize metal oxides for OXZEO syngas conversion,"said Prof. PAN.

　　Water splitting is one of renewable and environmentally-friendly energy sources.
　　Understanding the reactions between water molecules and isolated metal atoms/clusters, which can boost catalytic performance, is helpful to reveal the microscopic mechanisms of water splitting at molecular level. However, the experimental investigation of the reactions between water molecules and neutral metals is challenging due to the neutral clusters, lack of charges, are hard to be detected.
　　Recently, a research team led by Prof. JIANG Ling and Dr. LI Gang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences studied the reactions of water with neutral vanadium (V) dimer by using a size-specific infrared-vacuum ultraviolet spectroscopy, and realized water splitting.
　　This study was published in The Journal of Physical Chemistry Letters on April 17.
　　The researchers measured infrared spectra for the neutral V2O3H4 and V2O4H6 complex in the 2800-4100 cm-1 spectral region by recently-developed infrared spectroscopy using a tunable vacuum ultraviolet free electron laser (VUV-FEL).
　　They found that V2O3H4 and V2O4H6 had unexpected V2(μ2-OH)(μ2-H)(η1-OH)2 and V2(μ2-OH)2(η1-H)2(η1-OH)2 structures, indicating the exist of water splitting. Moreover, they indicated that the water splitting by V2 was both thermodynamically exothermic and kinetically facile in the gas phase.
　　"Our study provides new avenues toward systematic understanding of water splitting by a large variety of single-cluster catalysts," said Prof. JIANG.

　　Multi-electron reaction is defined as a reaction in which more than one electron is transferred per active materials molecule. VOPO4, a typical class of multi-electron reaction cathode materials with V4+/V5+ and V3+/V4+ multiple redox couples, possesses a higher potential with the introduction of more electronegative (PO4)3- anion, which can provide enhanced energy density.
　　However, the vanadium phosphates suffer from unsatisfactory performance, especially for high rate capability due to the bulk diffusion process and low intrinsic electrical conductivity.
　　Recently, a research team led by Prof. WU Zhong-Shuai from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has developed a high-performance 2D pseudocapacitive multi-electron reaction lithium storage materials via V4+ defect engineering for solid-state lithium metal batteries with high energy density and high power density.
　　This study was published in Advanced Energy Materials on April 9.
　　Schematic of Li||ETPTA-LiClO4-SSE||VOPO4 solid-state lithium metal battery and the corresponding Ragone plot（Image by XING FeiFei）
　　The researchers realized the high-rate pseudocapacitive cathode with multi-electron reaction chemistry by regulating V4+ defect in VOPO4. The as-prepared 2D VOPO4/graphene nanosheets not only had an ultrathin nanosheet structure to improve electronic and ionic conductivity, but also adjusted the uniformity of multi-electron reactions and reduced polarization by controlling the content of V4+ defects.
　　The pseudocapacitive multi-electron reaction cathode exhibited a high capacity of 313 mAh g-1 at 0.1 C and maintained a capacity of 116 mAh g-1 at an ultrafast rate of 50 C.
　　The researchers further synthesized a novel UV-curable solid electrolyte (ETPTA-LiClO4-SSE), which had an ion conductivity of 0.99 mS cm-1 at room temperature. This was much higher than that of polyethylene oxide solid electrolytes (~10-6 S cm-1). The assembled Li||ETPTA-LiClO4-SSE||VOPO4 solid-state lithium metal battery presented a high energy density of 85.4 Wh kg-1 and a high power density of 2.3 kW kg-1.
　　What's more, the as-assembled solid-state lithium metal batteries pouch cell displayed good flexibility and safety.
　　"Our study provide a new avenue for the development of 2D pseudocapacitive fast-charging cathodes with multi-electron chemistry for high specific energy and high power lithium metal batteries," said Prof. WU.
　　This study was supported by the National Natural Science Foundation of China, and DICP Innovation Fund.

　　Yin-Yang theory is an ancient Chinese philosophy in which Yin-Yang forces are interdependent and work in opposition to each other to create balance.
　　Recently, inspired by this ancient theory, a research team led by Prof. GUO Xin and Prof. LI Can from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has revealed the origin of the stability of Dion–Jacobson (DJ) phase two-dimensional (2D) perovskite materials.
　　Their findings were published in Joule on April 12.
　　DJ 2D perovskites, a class of organic–inorganic hybrid perovskite materials, have been widely used for various optoelectronic applications.
　　Compared to traditional 3D perovskites with intrinsically low stability, 2D perovskites including the Ruddlesden–Popper (RP) phase and DJ phase are more attractive due to their enhanced stability, especially DJ 2D perovskites based on organic diammonium cations and inorganic lead iodide octahedra, which have higher structural stability than RP ones.
　　However, some of DJ 2D perovskites are not robust and even more easily degraded than RP 2D counterparts, which has led to a controversy over their stability. These contradictory research results have impelled scientists to clearly elucidate the stability mechanism of DJ 2D perovskites with different diammonium cations.
　　In this study, the researchers demonstrated that the stability of DJ 2D perovskites was determined by the rigidity of organic diammonium cations, which could induce co-adaptation of organic and inorganic components to stabilize the 2D structure. Specifically, the medium cation rigidity allowed for organic diammoniums and inorganic octahedra to regulate their geometries in mutual accommodation in order to reach a stabilized state.
　　This mechanism may provide guidance for researchers who want to consciously manipulate the stability of DJ 2D perovskites by adjusting cation rigidity.
　　"Similar to the two parties in the Yin-Yang theory, organic cations and inorganic octahedra in DJ 2D perovskites are interconnected with alternating hydrogen bonds and when both parts can adjust their geometries to adapt to each other, strong connections are desirable," said Prof. GUO. "In this way, organic cations with moderate rigidity would play a critical role in the process of intercoordination because they have a certain degree of freedom to regulate the geometry and the inorganic part can correspondingly change its configuration as well."

　　Materials that can conduct negatively charged hydrogen atoms in ambient conditions would pave the way for advanced clean energy storage and electrochemical conversion technologies. A research team from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) demonstrated a technique that enables a room-temperature all-solid-state hydride cell by introducing and exploiting defects in the lattice structure of rare earth hydrides.
　　Their study was published in Nature on April 5.
　　Solid materials that conduct lithium, sodium and hydrogen cations have been used in batteries and fuel cells. Under certain conditions, some of the materials transition to superionic states where ions move as fast as they do in liquids by skipping through the rigid crystal structure. This phenomenon is advantageous for chemical and energy conversions as it allows ions to move without a liquid or soft membrane to separate the electrodes. However, few solid-state materials can reach this state under ambient conditions.
　　"Materials that exhibit superionic conduction at ambient conditions would provide huge opportunities for constructing brand new all-solid-state hydride batteries, fuel cells and electrochemical cells for the storage and conversion of clean energy," said Prof. CHEN Ping, study author from DICP.
　　With strong reducibility and high redox potential, hydride ion (H-) conductors have emerged as promising candidates for this technology. Several H- conductors have already been developed in recent years, including alkaline earth metal hydrides and oxyhydrides of alkaline earth and rare earth metals, which are known for fast hydrogen migration. But none of the materials developed could achieve superionic conduction at ambient conditions —until the DICP team took a new approach.
　　The DICP research team targeted the structure and morphology of trihydrides — hyrdrides containing three atoms of hydrogen per molecule — of certain rare earth elements (REHx), including Lanthanum (La).
　　Strategies to enhance electronic conductivities typically seek to diminish crystallographic imperfections for applications like metallic nanowire interconnects and nanostructured photovoltaic semiconductors. In this study, however, the research team purposely created abundant discrete nanosized grains and lattice defects to disturb the path of electron transport in REHx and suppress the electronic conductivity. This is different from engineering conventional materials for ion conduction, which relies upon the consistent structure of high crystallinity.
　　The research team observed how H- ions diffused easily in REHx lattices by hopping between octahedral and tetrahedral sites in the crystal and across interfaces or grain boundaries. Electrons, on the other hand, encountered substantial scattering at grain boundaries, particle surfaces and other traps, which brought down the electronic conductivities by three to five orders of magnitude from those of their well-crystallized counterparts.
　　"By creating nano-sized grains, defects and other crystalline mismatched zones in a known ionic-electronic mixed conductor, we demonstrated that the electronic conductivity of LaHx (x ≈ 2.94) can be largely suppressed by five orders of magnitude," said CHEN. "Engineering such a material could transform LaHx into a pure hydride ion conductor with record high conductivities in the temperature range of -40 to 80 ℃."
　　The researchers effectively suppressed electron conduction of LaHx by decreasing the particle size and distorting the lattice via high-energy ball milling, which involves subjecting the material to high-energy collisions. With fast H- conduction and a high ion transfer number, the deformed LaHx material would enable a hydride ion battery to operate at room temperature or lower.
　　"This work demonstrates the effectiveness of lattice deformation in suppressing electron conduction in REHx," said CHEN.
　　The researchers plan to explore the physics underneath the phenomenon and extend the method developed in this study to other hydride materials to broaden the material scope for pure H- conductors.
　　"Our near-term goal is to demonstrate a brand new all-solid-state hydride ion battery that is of practical potential," said CHEN.
　　This work was jointly supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, Youth Innovation Promotion
　　Association CAS and the Liaoning Revitalization Talents Program.
　　Other contributors include ZHANG Weijin, CUI Jirong, WANG Shangshang, CAO Hujun, JIANG Qike, GUO Jianping and HE Teng from DICP; WU Anan from Xiamen University and XIA Yuanhua from the China Academy of Engineering Physics.